XAllocNamedColor
XAllocColor(3X11) XLIB FUNCTIONS XAllocColor(3X11)
NAME
XAllocColor, XAllocNamedColor, XAllocColorCells, XAllocColorPlanes,
XFreeColors - allocate and free colors
SYNTAX
Status XAllocColor(Display *display, Colormap colormap, XColor
*screen_in_out);
Status XAllocNamedColor(Display *display, Colormap colormap, char
*color_name, XColor *screen_def_return, XColor
*exact_def_return);
Status XAllocColorCells(Display *display, Colormap colormap, Bool con-
tig, unsigned longplane_masks_return[], unsigned int nplanes,
unsigned long pixels_return[], unsigned int npixels);
Status XAllocColorPlanes(Display *display, Colormap colormap, Bool
contig, unsigned long pixels_return[], int ncolors, int nreds,
int ngreens, int nblues, unsigned long *rmask_return, unsigned
long *gmask_return, unsigned long *bmask_return);
int XFreeColors(Display *display, Colormap colormap, unsigned long
pixels[], int npixels, unsigned long planes);
color_name
Specifies the color name string (for example, red) whose
color definition structure you want returned.
colormap Specifies the colormap.
contig Specifies a Boolean value that indicates whether the planes
must be contiguous.
display Specifies the connection to the X server.
exact_def_return
Returns the exact RGB values.
ncolors Specifies the number of pixel values that are to be returned
in the pixels_return array.
npixels Specifies the number of pixels.
nplanes Specifies the number of plane masks that are to be returned
in the plane masks array.
nreds
ngreens
nblues
Specify the number of red, green, and blue planes. The
value you pass must be nonnegative.
pixels Specifies an array of pixel values.
pixels_return
Returns an array of pixel values.
plane_mask_return
Returns an array of plane masks.
planes Specifies the planes you want to free.
rmask_return
gmask_return
bmask_return
Return bit masks for the red, green, and blue planes.
screen_def_return
Returns the closest RGB values provided by the hardware.
screen_in_out
Specifies and returns the values actually used in the col-
ormap.
DESCRIPTION
The XAllocColor function allocates a read-only colormap entry corre-
sponding to the closest RGB value supported by the hardware. XAlloc-
Color returns the pixel value of the color closest to the specified
RGB elements supported by the hardware and returns the RGB value actu-
ally used. The corresponding colormap cell is read-only. In addi-
tion, XAllocColor returns nonzero if it succeeded or zero if it
failed. Multiple clients that request the same effective RGB value
can be assigned the same read-only entry, thus allowing entries to be
shared. When the last client deallocates a shared cell, it is deallo-
cated. XAllocColor does not use or affect the flags in the XColor
structure.
XAllocColor can generate a BadColor error.
The XAllocNamedColor function looks up the named color with respect to
the screen that is associated with the specified colormap. It returns
both the exact database definition and the closest color supported by
the screen. The allocated color cell is read-only. The pixel value
is returned in screen_def_return. If the color name is not in the
Host Portable Character Encoding, the result is implementation-depen-
dent. Use of uppercase or lowercase does not matter. If
screen_def_return and exact_def_return point to the same structure,
the pixel field will be set correctly, but the color values are unde-
fined. XAllocNamedColor returns nonzero if a cell is allocated; oth-
erwise, it returns zero.
XAllocNamedColor can generate a BadColor error.
The XAllocColorCells function allocates read/write color cells. The
number of colors must be positive and the number of planes nonnega-
tive, or a BadValue error results. If ncolors and nplanes are
requested, then ncolors pixels and nplane plane masks are returned.
No mask will have any bits set to 1 in common with any other mask or
with any of the pixels. By ORing together each pixel with zero or
more masks, ncolors * 2nplanes distinct pixels can be produced. All
of these are allocated writable by the request. For GrayScale or
PseudoColor, each mask has exactly one bit set to 1. For DirectColor,
each has exactly three bits set to 1. If contig is True and if all
masks are ORed together, a single contiguous set of bits set to 1 will
be formed for GrayScale or PseudoColor and three contiguous sets of
bits set to 1 (one within each pixel subfield) for DirectColor. The
RGB values of the allocated entries are undefined. XAllocColorCells
returns nonzero if it succeeded or zero if it failed.
XAllocColorCells can generate BadColor and BadValue errors.
The specified ncolors must be positive; and nreds, ngreens, and nblues
must be nonnegative, or a BadValue error results. If ncolors colors,
nreds reds, ngreens greens, and nblues blues are requested, ncolors
pixels are returned; and the masks have nreds, ngreens, and nblues
bits set to 1, respectively. If contig is True, each mask will have a
contiguous set of bits set to 1. No mask will have any bits set to 1
in common with any other mask or with any of the pixels. For
DirectColor, each mask will lie within the corresponding pixel sub-
field. By ORing together subsets of masks with each pixel value,
ncolors * 2(nreds+ngreens+nblues) distinct pixel values can be pro-
duced. All of these are allocated by the request. However, in the
colormap, there are only ncolors * 2nreds independent red entries,
ncolors * 2ngreens independent green entries, and ncolors * 2nblues
independent blue entries. This is true even for PseudoColor. When
the colormap entry of a pixel value is changed (using XStoreColors,
XStoreColor, or XStoreNamedColor), the pixel is decomposed according
to the masks, and the corresponding independent entries are updated.
XAllocColorPlanes returns nonzero if it succeeded or zero if it
failed.
XAllocColorPlanes can generate BadColor and BadValue errors.
The XFreeColors function frees the cells represented by pixels whose
values are in the pixels array. The planes argument should not have
any bits set to 1 in common with any of the pixels. The set of all
pixels is produced by ORing together subsets of the planes argument
with the pixels. The request frees all of these pixels that were
allocated by the client (using XAllocColor, XAllocNamedColor, XAlloc-
ColorCells, and XAllocColorPlanes). Note that freeing an individual
pixel obtained from XAllocColorPlanes may not actually allow it to be
reused until all of its related pixels are also freed. Similarly, a
read-only entry is not actually freed until it has been freed by all
clients, and if a client allocates the same read-only entry multiple
times, it must free the entry that many times before the entry is
actually freed.
All specified pixels that are allocated by the client in the colormap
are freed, even if one or more pixels produce an error. If a speci-
fied pixel is not a valid index into the colormap, a BadValue error
results. If a specified pixel is not allocated by the client (that
is, is unallocated or is only allocated by another client) or if the
colormap was created with all entries writable (by passing AllocAll to
XCreateColormap), a BadAccess error results. If more than one pixel
is in error, the one that gets reported is arbitrary.
XFreeColors can generate BadAccess, BadColor, and BadValue errors.
DIAGNOSTICS
BadAccess A client attempted to free a color map entry that it did not
already allocate.
BadAccess A client attempted to store into a read-only color map
entry.
BadColor A value for a Colormap argument does not name a defined Col-
ormap.
BadValue Some numeric value falls outside the range of values
accepted by the request. Unless a specific range is speci-
fied for an argument, the full range defined by the argu-
ment’s type is accepted. Any argument defined as a set of
alternatives can generate this error.
SEE ALSO
XCreateColormap(3X11), XQueryColor(3X11), XStoreColors(3X11)
Xlib - C Language X Interface
XAllocColor(3X11)
